Multiple density-dependent processes shape the dynamics of a spatially structured amphibian population.

Area of Science:

• Ecology
• Population Dynamics
• Conservation Biology

Background:

• Spatially structured populations (SSP) dynamics are influenced by local (births, deaths) and inter-population (dispersal) processes.
• Density dependence critically affects demographic traits and population growth at both patch and SSP scales.
• Few studies simultaneously examine density-dependent effects on local populations and SSP-level dispersal.

Purpose of the Study:

• To investigate density-dependent effects on pond-level survival, population growth, and SSP-level dispersal.
• To analyze these effects in a pond-breeding amphibian, the great crested newt (Triturus cristatus).
• To understand contrasting density effects on demographic parameters and dispersal within SSPs.

Main Methods:

• Utilized 20 years of capture-recapture (CR) data from 12 experimental ponds.
• Employed CR multievent models to estimate survival and dispersal rates as functions of pond distance and density.
• Applied state-space time series models to assess density effects on pond population growth.

Main Results:

• Observed a positive density-dependent effect on survival rates.
• Found a negative density-dependent effect on dispersal (departure) rates.
• Demonstrated that population growth was negatively related to density across all ponds.

Conclusions:

• Density exhibits multiple and contrasting effects on demographic parameters and growth rates within local populations and on dispersal in SSPs.
• Findings highlight the complex interplay between density dependence, life-history strategies, and life-history stages in amphibians.
• Emphasizes the need for comprehensive understanding of density dependence for effective conservation and management of SSPs.